Immunohistochemical staining with deltaNp63 is useful for distinguishing the squamous cell component of adenosquamous cell carcinoma of the lung.

BACKGROUND DeltaNp63 is an isoform of the p53 homolog p63, which lacks an amino-terminal transactivation domain. The aim of this study was to detect the deltaNp63 expression in the squamous carcinoma component of adenosquamous carcinoma and evaluate its usefulness as a specific squamous carcinoma marker. PATIENTS AND METHODS Immunohistochemistry was used to analyze the protein expression of deltaNp63 and high molecular weight cytokeratin in paraffin-embedded tumor samples from 17 patients with well-characterized adenosquamous carcinoma. RESULTS Of 17 cases, 13 (76.5%) and 14 (82.4%) cases showed positive staining for deltaNp63 and HMWCK in the tumor cells, respectively. It was easy to discriminate the squamous carcinoma and adenocarcinoma components in all tumors. Interestingly, positive expression of deltaNp63 was detected in one case with a negative expression of HMWCK. CONCLUSION These findings indicated that the deltaNp63 status was useful for distinguishing squamous carcinoma from adenocarcinoma in formalin-postfixed adenosquamous carcinoma specimens.